Vikings follows the adventures of Ragnar Lothbrok, the greatest hero of his age. The series tells the sagas of Ragnar's band of Viking brothers and his family, as he rises to become King of the Viking tribes. As well as being a fearless warrior, Ragnar embodies the Norse traditions of devotion to the gods. Legend has it that he was a direct descendant of Odin, the god of war and warriors.

Ragnar, weak and still hurt, must meet the Earl head-on after it comes to light that Rollo has been tortured on Haraldson’s orders. The two men will come together face to face with a single outcome possible: Only one man will leave this fight alive.

The traditional pilgrimage to Uppsala to thank the gods brings a torrent of emotions for Ragnar, Lagertha, and Athelstan. Ragnar, pulling farther away from his wife goes to make peace with the death of his unborn son. Lagertha, still reeling from her miscarriage, wants to find out from the gods if more sons are in her future. As the Vikings come together to sacrifice and give thanks to their gods, Athelstan discovers just how strong his Christian faith still is.

Ragnar travels to Götaland to help King Horik resolve a land dispute with the area's leader, Jarl Borg. Meanwhile, sickness infects the village of Kattegat, and the people look to Lagertha to help them appease the gods.